Field
Embodiments described generally relate to methods for making lignocellulose composite products. More particularly, such embodiments relate to methods for making lignocellulose composite products with one or more polyphenolic materials and one or more free radical precursors.
Description of the Related Art
The production of lignocellulose composite products requires an adhesive or binder to bond the discrete, particulates, fibers, veneers, or other substrates to one another. Typical lignocellulose composite products include particleboard, fiberboard, plywood, and the like. Conventional binders used in the production of these products frequently contain formaldehyde based resins such as urea-formaldehyde (UF), melamine-formaldehyde (MF), melamine-urea-formaldehyde (MUF), and phenol-formaldehyde (PF) binders. While formaldehyde based resins produce finished products having desirable properties, such as strength, these binders also release formaldehyde into the environment during the production of the binder, curing of the binder/composite product, as well as, from the final product made using the binder.
Various techniques have been used to reduce the amount of formaldehyde released from formaldehyde based resins. For example, the addition of formaldehyde scavengers to the resin and/or various modifications to the particular synthesis steps used to make the formaldehyde based resin, such as the addition of urea as a reactant late in the binder synthesis, are often used in an attempt to reduce formaldehyde emission. These attempts to reduce formaldehyde emission, however, are accompanied with undesirable effects such as longer cure time, reduced resin shelf-life, reduced product strength, reduced tolerance for processing variations, and/or inferior moisture resistance.
There is a need, therefore, for improved methods for making lignocellulose containing composite products having reduced or no formaldehyde emission.